1. Field of the Invention
The present invention relates generally to apparatus and method for supplying electric power to the starter motor of a UPS system when line power fails. More specifically, the present invention teaches an apparatus for using kinetic energy stored in the rotating elements of a UPS motor generator to supply the power required for the starter motor system of an internal combustion backup generator.
2. Description of the Related Art
The present application for a batteryless starter system may be more easily understood if it is read with the uninterruptable power supply systems taught by U.S. Pat. No. 4,460,834 issued Jul. 7, 1984 and UPS Cogeneration System, U.S. Pat. No. 4,686,375 issued Aug. 11, 1987.
Virtually all prior art UPS systems, which use an internal combustion engine to drive a standby generator, including those taught by U.S. Pat. Nos. 4,460,834 and 4,686,375, require the use of a chemical storage battery and related charging and control circuits. The present inventor, form his experience in building and installing numerous UPS systems, and believes that those skilled in the art have gone to great lengths to deal with the many problems caused by the use of a chemical storage battery to supply the brief burst of power required to run the starter motor of the internal combustion engine of a backup generator in a UPS system. Persons skilled in the art have used sealed chemical cells of expensive exotic materials such as lithium and silver rather than ordinary lead-acid storage batteries and have done much research to make these batteries more dependable, smaller, less expensive and less prone to degenerative failure. All chemical storage batteries used in UPS systems must be both charged and replaced. They must be charged on a regular schedule in order to maintain enough of a charge in the battery to dependably operate the starter motor of the backup generator. Some experts in this art teach that UPS batteries should be completely discharged and then recharged on a regular cycle as part of the ordinary maintenance of the UPS system, in order to maximize total battery life. These batteries must also be replaced from time to time to insure that the battery is fresh enough to be able to hold a charge between the routine charging cycles dictated by normal operation and maintenance of the UPS system.
The batteries that power the starter motor for standby electric generators need to be kept as small, light and inexpensive as possible for the sake of economy. This set of conditions, i.e. small and light, are design criteria that conflict directly with the battery's need to be of large capacity to dependably supply a large flow of current infrequently to actually operate backup generator starter system. Charging a chemical battery many times can cause warpage of the plates that form the cells of the battery. When a large load is placed across a battery, high temperatures and mechanical stresses are generated between these plates. If a battery is marginal due to repeated chargings cycles, or is near the end of its storage life, it can fail because of these thermal and mechanical stresses, rendering the UPS system inoperable. In order to avoid this problem, some UPS systems require redundant starter battery sets with automatic switchover means in case one battery set fails. The maintenance and replacement of these batteries is expensive. Malfunction of batteries and their associated charging equipment is a common reason for UPS system failure.
Additionally, some small UPS systems have had redundant backup recoil starters. If the battery driven starter motor fails to start the auxiliary generator, it may be cranked by hand or by a mechanical spring. This is only practical for very small generators. Large backup generators rely either on an expensive program of frequent battery replacement, or redundant chemical battery sets to insure that they will start reliably in an emergency.